The invention relates to an air intake system for internal combustion engines, particularly for V engines.
From German Patent 197 56 332, an air intake channel system is known wherein the length of several air intake channels, each of which is connectible with a cylinder of an internal combustion engine, can be varied smoothly. To this end, the helically configured intake channels are arranged next to each other. Each helical air intake channel comprises an air inlet opening connected with a central inner portion of the air intake system through which air inlet opening the air enters into the helical channel and is guided to the respective cylinder after having flown through the helical channel. Within the central portion, a tubular channel portion is arranged which forms the inner wall of the helical channel and comprises the air inlet opening. The tubular channel portion is pivotally arranged so that the position of the air inlet opening can be varied. In this manner, the length of the air intake channel, i.e., the distance between air inlet opening and air outlet opening to be flown through by the air, can be varied smoothly by pivoting the tubular channel portion.
The individual channel portions forming the intake channels are arranged adjacent to each other or in a stack, the configured air intake channels being alternately connected with the one or the other row of cylinders of the V motor. To pivot the inner pivotal channel portions, they are connected to a pivot axis. Thus, each air intake channel is substantially formed by a stationary channel portion and a pivotal channel portion. The tubular pivotal channel portion is supported in a recess of the stationary channel portion. The recess in the stationary channel portion comprises a radial and an axial abutment surface. Upon pivoting the pivotal channel portion, the pivotal channel portion slides on the radial as well as on the axial abutment surface. Since the two channel portions are made of plastics, the sliding occurs between two plastics parts. The mutual friction between plastic parts results in great wear. Further, no sufficient sealing between adjacent air intake channels is guaranteed because of the mutual friction of plastics parts.
From German Patent 195 28 014, an air intake channel system with a stationary and a pivotal channel portion for varying the length of the air intake channel is known as well. To seal the pivotal channel portion with respect to the stationary channel portion, it describes a labyrinth-like configuration of the portions sliding upon each other. Due to this labyrinth sealing, the sealing effect between the two channel portions can be improved, but two plastics parts do still slide upon each other. German Patent 195 28 014 further suggests to provide a radially or axially extending sealing disc instead of a labyrinth sealing. Two plastics parts still slide upon each other in these embodiments as well.
It is the object of the present invention to reduce wear in an air intake channel system with a good sealing effect between channel portions pivotal with respect to each other.
This object is solved, according to the invention, with the features of claim 1.
According to the invention, a slide element is provided in the recess of the one channel portion comprising a radial and an axial abutment surface for receiving the pivotal channel portion, said slide element abutting on the radial as well as on the axial abutment surface. Thus, the slide element with an, e.g., L-shaped cross section is both axially and radially arranged between the two channel portions. Thus, it is avoided that the two channel portions touch each other in the region of the recess of the one channel portion wherein the other channel portion is supported. The two channel portions only touch the slide element. Preferably, the slide element is made of metal so that only low sliding friction occurs between the two plastics channel portions and the slide element. Additionally, the slide element according to the invention acts as a labyrinth sealing.
Preferably, the slide element is laid such into the recess of a channel portion that it is freely rotatable. Since the slide element has no fast connection to any of the channel portions, the friction between the respective channel portions and the slide element and thus also the wear, particularly with different forces acting in the recess, are reduced.
To improve the sealing effect of the slide element, one of the two channel portions comprises a groove to receive the slide element. To this end, the slide element is provided with a retaining lug projecting into the groove. In this embodiment, the cross section of the slide element is preferably substantially C-shaped. The combination of slide element and groove corresponds to a labyrinth sealing.
Preferably, the slide elements are held by a groove provided in the pivotal channel portion. Thus, it is possible to preassemble the slide elements on the pivotal channel portions. This guarantees a simple and safe mounting of the respective channel portions.